An endoscope is an elongated tubular structure which is inserted into body cavities to examine them. The endoscope includes a telescope with an objective lens at its distal end. The telescope usually includes an image-forwarding system. In rigid endoscopes it is a series of spaced-apart lenses. In flexible endoscopes it is a bundle of tiny optical fibers assembled coherently to forward the image. Some endoscopes include a camera means, such as a CCD or CMOS image sensor, in the distal portion and forward the image electronically. This invention is applicable to all types of image forwarding systems.
Many endoscopes view only directly forward. Others feature fixed or movable reflectors in the distal portion to allow off-axis viewing. Some, most commonly flexible types, feature actuated bending portions at the distal end. This invention is applicable to all types of axial, non-axial, and variable direction of view endoscopes.
At the proximal end of the image-forwarding system, some endoscopes include an ocular lens which creates a virtual image for direct human visualization. Often a camera means, such as a CCD or CMOS chip, is connected to the endoscope. It receives the image and produces a signal for a video display. Some endoscopes have a camera means built directly into the endoscope.
While surgeons can, and often do, look directly into the endoscope through an ocular lens, it has become more common for them to use an attached video camera and observe an image on a video screen. In a surgical or diagnostic procedure, the surgeon manipulates the endoscope. He may cause it to pitch about a lateral axis or roll about a longitudinal axis. As these manipulations occur to an endoscope with an attached camera, the camera faithfully relates what it sees, with its own upright axis displayed as the upright axis of the image on the display. This often results in rotation of the viewed image.
That is the very problem. As the image rotates, the surgeon loses track of what is actually up and down inside the endoscopic cavity. This disorientation is one of endoscopy's greatest enemies and has lead to severe mistakes such as the snipping of optical nerves which during a procedure were believed to be a different part of the anatomy. When surgical procedures where open rather than endoscopic, the surgeon could see the anatomy directly and therefore did not have a disorientation problem. However, during an endoscopic procedure the surgeon's viewpoint is different from the viewpoint of the endoscope, and the surgeon must continuously try to correlate his own mental picture of the anatomy with the endoscopic picture on the display. In doing this, the need to know what is up and down inside the endoscopic cavity is so strong that it has become common for surgeons to observe the flow direction of fluid droplets on the endoscope cover window or search for pooling blood in order to get a sense of direction inside the cavity. Aside from being important for distinguishing anatomical features which may look similar, knowing the up-direction also helps in understanding the endoscope's position relative to the surrounding anatomy. Ideally, the surgeon would be able to relate to the endoscopic cavity as if his own eyes were actually inside the cavity.
An attempted solution to this problem is proposed in U.S. Pat. No. 5,307,804 to Bonnet (1994), which is incorporated herein by reference in its entirety. An object of this invention was to maintain the orientation of an endoscopic image without the use of electronic sensing and positioning devices. A pendulum fixed to a camera is rotatably attached to an endoscope. The pendulum maintains an orientation with respect to gravity around the endoscope longitudinal axis. As the endoscope rotates, the pendulum causes the camera to rotate in the opposite direction relative to the endoscope. This is intended to maintain the image in a proper orientation.
An endoscope with rotational orientation correction is also suggested in U.S. Pat. No. 5,899,851 to Koninckx (1999), which is incorporated herein by reference in its entirety. An electronic rotation pick-up means responsive to gravity senses rotation of a camera around the endoscope longitudinal axis. An image rotator rotates the camera image according to the rotation signal from the rotation pick-up means.
Another endoscope and camera system with rotational orientation correction is disclosed in U.S. Pat. No. 6,097,423 to Mattsson-Boze, et al. (2000), which is incorporated herein by reference in its entirety. Electronic sensing and positioning devices combine to sense and correct the rotation of a camera rotatably attached to an endoscope. An accelerometer fixed to the camera serves as an electronic rotation pick-up means responsive to gravity. A motor rotates the camera according to signals from the accelerometer. This accelerometer and motor system is functionally equivalent to the pendulum described by Bonnet. While the pendulum relies on the force of gravity to rotate, the accelerometer sensitively measures gravity and the motor rotates the assembly accordingly. The system can therefore be thought of as an electro mechanical pendulum. Mattsson-Boze also recognizes rotation of the image by electronic manipulation to correct the image orientation, but actively discourages this practice for several reasons.
U.S. Pat. No. 6,471,637 to Green, et al. (2002), which is incorporated herein by reference in its entirety, discloses the same apparatus as disclosed in Mattsson-Boze, and suggests two alternative methods for image rotation. In the first method, an optical image rotator is used instead of a rotating camera. In the second method, electronic manipulation is used to correct the image orientation. Also, one or more gyroscopes are suggested as alternative electronic rotation pick-up means.
U.S. patent application Ser. No. 2002/0161280 by Chatenever, et al. which is Incorporated herein by reference in its entirety, discloses the same apparatus as disclosed in Mattsson-Boze and in Green, and suggests two alternative methods for electronic rotation pick-up. In the first method, image analysis is used to compute a rotational signal. In the second method, a machine vision system is used to compute a rotation signal.
U.S. Patent Application Nos. 2005/0228230 and 2005/0154260 by Schara et al., which are incorporated herein by reference in their entirety, teach general solutions to the image orientation problem. Unlike the above disclosures, these disclosures can provide a gravity-leveled endoscopic image for all scope types and configurations, regardless of endoscope pitch and roll and any line of sight offset from the axis of the endoscope.
All of the above solutions teach only automatic reorienting and leveling of the endoscopic image. From market surveys and discussions with surgeons in different disciplines it has become apparent that even just an indicator of vertical without reorientation of the endoscopic image would be very useful. Surgeons have become accustomed to reorienting the endoscopic camera manually during a procedure and do not necessarily require or even want the image automatically corrected for them. Simply providing an indicator of vertical would allow the surgeons to keep the practice of adjusting the camera themselves and at the same time give a visual key of how much the camera must be rotated in order to achieve a truly upright image. Alternately, the surgeon could elect to maintain a current camera orientation but would with an indicator at least be able to see which direction was up. This is especially relevant with the latest chip-in-tip endoscopes which have a distal camera that cannot be rotated.
Also, except for U.S. Patent Applications Nos. 2005/0228230 and 2005/0154260 by Schara et al, all of the above solutions compensate only for roll about the longitudinal axis, and provide a rotationally corrected image only for axial viewing endoscopes. They provide an approximation of the correct orientation for slightly oblique viewing endoscopes held near horizontal, but only Schara et al. teach a solution that is correct for straight, oblique, side, retro, and variable direction of view endoscopes. The current practice in endoscopy is for the surgeon to try to keep the image vertical by rotating the proximal camera head such that its roll about the endoscope axis stays level with the horizon. This is done regardless of the type of scope being used, whether straight, oblique, or flexible. The widespread misunderstanding here is that this practice keeps the image leveled. It in fact only provides a leveled image in the case of a rigid straight viewing endoscope. For any other scope type this practice does not provide a leveled image and is misleading because what is believed to be a leveled image actually is not.
Thus, it is an object of this invention to provide an indicator of the correct upright orientation (with respect to the viewer) of a viewed image from an endoscope. It is an additional object of this invention to be applicable to any axial, oblique, side, or retro viewing endoscope as well as any endoscope with a variable direction of view.